Research has shown that Alpha brain waves (typically measured between 10 and 12 Hz in adult humans)) can act as an inhibitor to detecting visual stimuli. For example, the effects of Alpha brain waves on stimulus recognition are discussed in the articles Mathewson, K. E., et al. “To See or Not to See: Prestimulus α Phase Predicts Visual Awareness.” Journal of Neuroscience 29.9 (2009): 2725-732 and Mathewson, Kyle E., et al, “Making Waves in the Stream of Consciousness: Entraining Oscillations in EEG Alpha and Fluctuations in Visual Awareness with Rhythmic Visual Stimulation.” Journal of Cognitive Neuroscience 24.12 (2012): 2321-333, both of which are hereby incorporated herein by reference. That is, a person's ability to detect (e.g., notice) a visual stimulus such as an image on a display is improved during particular phases of an Alpha wave.